Misawa Homes Institute of Research and Development Co., Ltd.Micro-climate Design that Fully Utilizes Wind and Sunlight Becomes Reality by Combining Conventional Solution Approaches with the Latest Computational Technology

[Vol. 1] An important part of environmental design for residential areas involves predicting temperature changes by simulating wind flows. Conventional environmental design practices used to primarily depend on the designers’ experience and intuition. Misawa Homes Institute of Research and Development Co., Ltd. (MHIRD) has implemented the micro-climate design concept, which considers the effects of both the climate and the natural features of each site. In micro-climate design, thermal fluid analyses are performed using computer simulations that result in high-performance residential house designs with enhanced living comfort. MHIRD was one of the first in industry to recognize the significance of including natural environmental conditions in the simulations. Dr. Yukari Hirayama (Picture 1), Chief Researcher at the MHIRD Environmental Energy Center, describes the role of simulations as a means to help create comfortable residential houses and cities of the future.

Thermal Fluid Analyses Used in Micro-climate Design

Misawa Homes Co., Ltd. is one of the largest developers of residential homes in Japan. They design, manufacture, build, and sell homes. MHIRD also undertakes research and development to improve their products. One important theme they have been researching is micro-climate design. Micro-climate design strives to produce a comfortable indoor environment throughout the year by taking advantage of the natural environment, climate and geographic features of the site. ‘Micro-climate’ is limited to the house and climate of the surrounding area. Some design concepts include using garden landscaping to change wind directions and prevent direct solar radiation. Software Cradle’s scSTREAM CFD software is the computational analysis tool used in the evaluation and design phases.

Prior to introducing scSTREAM 20 years ago, MHIRD asked Software Cradle to develop a function for analyzing the indoor thermal distribution as a function of outdoor environmental conditions. “The core challenge of promoting micro-climate design is how to combine the latest computational technology with conventional approaches that utilize wind and sunlight. We began using scSTREAM when we realized that temperature and air flow must be considered to properly evaluate the degree of comfort,” explains Dr. Hirayama.

MHIRD conducted measurements and post construction evaluations in collaboration with the Tokyo Institute of Technology. These were performed in the Miyazakidai area along the Den-en-toshi railway line in Kanagawa, Japan. One of the goals of this particular development project was to leave the forest as untouched as possible. Much of the planning involved evaluating characteristics of the existing green and geographical features. From research performed after tenants moved in, MHIRD found that residents stopped using their air-conditioners during the summers after three years. The positive effects of micro-climate design were also verified for the thermal radiation environment. To highlight the qualitative importance of micro-climate design, MHIRD started actively promoting residential houses with high natural ventilation efficiency using the slogan: ‘House with - 3.5 °C effective temperature’.

MHIRD adopted scSTREAM as the standard analytical tool to evaluate micro-climate designs for the development of CENTURY, a series of residential houses that ultimately received Good Design Award. MHIRD implemented a passive design that was well suited for the climate and natural features of the site while providing the flexibility to locally adjust the micro climate. MHIRD divided the entire nation into small climatic zones and prepared an operations manual for micro-climate designed buildings, which covers the micro climate of each zone. For the development of Marina East 21 Midorihama, a large residential area in Urayasu-shi (Chiba, Japan), Dr. Hiryama recalls: “As the wind from the sea is strong in the area, we wanted to make use of it, but we also realized the need to take shelter from it if we were to provide a comfortable living environment. We implemented designs that let the winds pass over the roofs of houses by appropriately locating hedge, trees and houses as a windbreak.” MHIRD started using ThermoRender, developed by A&A Co., Ltd., during this project and have continued using it, along with scSTREAM, to evaluate the effect on effective temperature.

Picture 2: M-Smart City Kumagaya

Performing Thermal Simulation of a Residential Area and its Surroundings

The concept of micro-climate design was implemented in a large scale for the development of M-Smart City Kumagaya (Saitama, Japan), which is planned to be completed in 2017. Kumagaya-shi in Saitama prefecture (Picture 2) is known for severely hot weather during the summer. With the desire to transform Kumagaya-shi into “a refreshing town,” micro-climate design has been implemented to take full advantage of wind flows while minimizing thermal radiation for the design of town sections and residential houses. The town section layout is designed to let mild breezes pass through green areas in the park, the ‘cool spot’, which lowers the effective temperature.

MHIRD also introduced ‘passive cooling technology’, which releases heat by water evaporation. Water retentive interlocking blocks are used for walkway and parking. The effect on surface temperature was evaluated by changing material properties on ThermoRender. Before introducing ThermoRender, designers had to manually input calculated surface temperatures to the computational model when performing the air flow analyses. “In 2015, ThermoRender and scSTREAM were coupled and now evaluation is much faster and easier than we even initially expected,” says Dr. Hirayama.

​​*All product and service names mentioned are registered trademarks or trademarks of their respective companies.
*Contents and specifications of products are as of September 16, 2015 and subject to change without notice. We shall not be held liable for any errors in figures and pictures, or any typographical errors in this brochure.

Company Details

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Misawa Homes Institute of Research and Development Co., Ltd.

Founded

1973

Main businesses

General research on residential home and living, evaluation, and system development services